By Lauren Haughey If you thought ‘I’m working late’ was the only cover-up for cheating, think again. A private investigator has unveiled the most unbelievable lies daters use to hide in plain sight while sneaking off to have secret rendezvous. Detective Leon Hart has caught more than 5,000 love rats in 15 years on the job, but claims nothing fails to surprise him when it comes to catching truth dodgers. “[One time] a man was suspected of cheating on his wife of 50 years, they had three children and seven grandchildren,” he recalled. “After utilising surveillance we identified that he was livin…